The main function of an isolator is to be the flexible link in a structure which is able to stop and/or damp vibration and shock loads from mechanical oscillations or shocks induced from the surroundings. The object that is to be damped is normally secured by one or more isolators, so that the total configuration has the properties that are desirable to isolate vibration and shock in the desired directions.
The background of the invention is a need for an isolator that has properties such as: low own weight, high damping, identical translatory damping properties in all axial directions, small size and long lifetime at low and high temperatures (−60 to +100° C.).
In, for example, the aircraft industry there are stringent requirements for isolators that are to damp shocks and vibration on critical components which are comprised in the basic functions of the aircraft, these being, for example, manoeuvring, navigation and engine functions. It is a particular requirement that isolators should have an own weight that is as small as possible and that isolators should function at a temperature of as low as at least −56° C. without their characteristics being essentially changed. Similarly, when it comes to heat, it is important that the isolator should function at a temperature as high as at least 100° C. (sun on hot days). These are actual requirements that must be met to comply with safety standards.
The invention is especially suitable for the mounting and installation of equipment that is to be protected from shocks and vibration in aircraft, boats and motor vehicles, but it may also have other areas of use.
Already existing isolators have good properties in one axis, for example, as taught in U.S. Pat. No. 4,783,038, or in one plane, as described in U.S. Pat. No. 5,791,636, but isolators according to the known solutions do not have the properties that are necessary if the isolator is to be able to take loads outside the specified axes/planes.
The first type of isolator to appear on the market is described in U.S. Pat. No. 4,783,038. In this isolator, the wire rope is secured in a wire rope series, the series being divided into two half series, and each of the half series having opposite inclinations such that a complete series compensates for lateral forces in the plane. A vertical load thus has stable properties in only one direction (compression) from a neutral position. This isolator does not have any additional wire rope loops that are secured at different inclinations in other directions than these two series, and therefore has completely different properties in all other directions than vertically downwards.
In U.S. Pat. No. 5,791,636, the symmetry in the plane is produced in that two loop series according to U.S. Pat. No. 4,783,038 are used that are placed diametrically 180 degrees opposite each other. This configuration will mean that identical properties will only be obtained in this plane which is parallel to the two loop series. For loads that act in directions out from this plane, the properties will be completely different.
The document also discloses that each loop series consists of two independent half series with opposite angles of inclination “a”, but that these are positioned separately on their respective side.
Moreover, the document describes an isolator that is mounted at each end of a centre piece (centre bar). This construction only has symmetrical properties in the axial direction of the centre bar from a neutral position, that is to say, in connection with linear motions along the centre bar.
Unlike U.S. Pat. No. 5,791,636, the invention solves the along-axis symmetry with a continuous loop series where each side of the loop series has different angles of inclination relative to the centre axis of the isolator.